TY  - JOUR
A1  - Mattern, Maximilian
A1  - von Reppert, Alexander
A1  - Zeuschner, Steffen Peer
A1  - Herzog, Marc
A1  - Pudell, Jan-Etienne
A1  - Bargheer, Matias
T1  - Concepts and use cases for picosecond ultrasonics with x-rays
JF  - Photoacoustics
N2  - This review discusses picosecond ultrasonics experiments using ultrashort hard x-ray probe pulses to extract the transient strain response of laser-excited nanoscopic structures from Bragg-peak shifts. This method provides direct, layer-specific, and quantitative information on the picosecond strain response for structures down to few-nm thickness. We model the transient strain using the elastic wave equation and express the driving stress using Gruneisen parameters stating that the laser-induced stress is proportional to energy density changes in the microscopic subsystems of the solid, i.e., electrons, phonons and spins. The laser-driven strain response can thus serve as an ultrafast proxy for local energy-density and temperature changes, but we emphasize the importance of the nanoscale morphology for an accurate interpretation due to the Poisson effect. The presented experimental use cases encompass ultrathin and opaque metal-heterostructures, continuous and granular nanolayers as well as negative thermal expansion materials, that each pose a challenge to established all-optical techniques.
KW  - Picosecond ultrasonics
KW  - Ultrafast x-ray diffraction
KW  - Ultrafast x-ray
KW  - scattering
KW  - Ultrafast photoacoustics
KW  - Nanoscale heat transfer
KW  - Negative
KW  - thermal expansion
Y1  - 2023
U6  - https://doi.org/10.1016/j.pacs.2023.100503
SN  - 2213-5979
VL  - 31
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Laquai, Rene
A1  - Gouraud, Fanny
A1  - Müller, Bernd Randolf
A1  - Huger, Marc
A1  - Chotard, Thierry
A1  - Antou, Guy
A1  - Bruno, Giovanni
T1  - Evolution of Thermal Microcracking in Refractory ZrO2-SiO2 after Application of External Loads at High Temperatures
JF  - Materials
N2  - Zirconia-based cast refractories are widely used for glass furnace applications. Since they have to withstand harsh chemical as well as thermo-mechanical environments, internal stresses and microcracking are often present in such materials under operating conditions (sometimes in excess of 1700 °C). We studied the evolution of thermal (CTE) and mechanical (Young’s modulus) properties as a function of temperature in a fused-cast refractory containing 94 wt.% of monoclinic ZrO2 and 6 wt.% of a silicate glassy phase. With the aid of X-ray refraction techniques (yielding the internal specific surface in materials), we also monitored the evolution of microcracking as a function of thermal cycles (crossing the martensitic phase transformation around 1000 °C) under externally applied stress. We found that external compressive stress leads to a strong decrease of the internal surface per unit volume, but a tensile load has a similar (though not so strong) effect. In agreement with existing literature on β-eucryptite microcracked ceramics, we could explain these phenomena by microcrack closure in the load direction in the compression case, and by microcrack propagation (rather than microcrack nucleation) under tensile conditions.
KW  - electro-fused zirconia
KW  - microcracking
KW  - synchrotron x-ray refraction radiography (SXRR)
KW  - thermal expansion
Y1  - 2019
U6  - https://doi.org/10.3390/ma12071017
SN  - 1996-1944
VL  - 12
IS  - 7
PB  - MDPI
CY  - Basel
ER  -